How to get a block to store data after being mined...

Hi everyone! I'm relatively new to MCreator. I'm building a mod that uses a battery to store forge energy and I'm wondering how to get the amount of stored energy to save when I mine the block. As of now, when I place the block again, all the stored energy is gone. Is there a way to store it in a variable or NBT data? I noticed there is a trigger for when the player starts breaking the block....  Any assistance or pointing me in the right direction would be greatly appreciated!